Car heater control



April 7, 1953 A. c. HOFFMAN CAR HEATER CONTROL 2 SHEETS--SHEET l FiledApril l5, 1949 iii M, .n Er W@ K c M n ATTORNEYS,

April 7, 1953 A. c. HOFFMAN 2,634,057

CAR HEATER CONTROL Filed April :L57` 1949 2 SHEETS--SHEET 2 254 5 6 7`89IOH I2I3 MINUTES INVENTOR. 4L/.4N 6I Hoff-M4N,

AT TORNEYS.

:that temperature and .other .heater and car air.

Patented Apr. 7, 1953' a -UNITED STATES PATENT OFFICE 2,634,057 CARHEATER CONTROL Allan Cf'Ho'ifman, Yellow Springs, Ohio, as-

signor to Vernay Laboratories Inc., Yellow Springs, hio,' a corporation`of Ohio Application April 13, 1949, Serial No.A 87,220

A i l i li'hs,invention relates to'a car heaterlcontrol Whichis adaptedto control a hot Waterheating system'for automobiles, whether'itY be ofthe type 'where fresh air is introduced into 'the car through aso-'called ram duct, or `oi the recircu- 'lating type.

Theadequate and lregular heating of the passenge'r compartment VVofan'automobile'presents numerous diiiicult problems. `In` the past car`lrie'atersjhave been controlled manually or' automatically ina numberrof Ways: `for example, a valve'was provided in the Water line in series'with the car heater andwas controlledfrom the instrument panel. Thisvalve was simply a mechanical device to regulate lthe flow of Watervthrough the heater and this iiow could be increased or ydecreaseddepending upon the temperature desired. As long as 4all conditions in-4volve'd'remained constant, this gave a good control "for 'the passengercompartment temperature. However, conditions do not 'remainconstantbecause engine speed, car speed, engine tvate'r temperature, Windlvelocity and direction are always changing. The result is 'that in a-control of this type the operator `has to adjust 'thecontrol valveconstantly in order to maintain Veven `a fairly satisfactory cartemperature.

Another system 'has been to endeavor to control thetemperaturein'thepassenger compartment by means of athermostat subjected tothe rIhisit'does network in` an automobile "for the' reason e i conditions Acanlchange `very much morerapidlyithan the ther- .;mostatfcancorrect'forzthem. The flow of Water vcan. `changeveryfrapidly withenginespeed and llikewisethe .temperature of vthe waterlcan changeM.very :rapidly with engine speed. Furthermore,

heat losses .from the passenger compartment can change extremely rapidlywhen the automobile ,goesffrom a .stati'c'condition to .movement at -a.veryhigh speed. .Attemptshave `been made .to

.correctythis condition by .causing theithermostat `still cycles, whichresults `in uncomfortable hot l'and cold blasts of air from theheater.

lvlorereoently car manufacturers.have` gone to the so-called ramductinwhich ,two ducts are :provided leading into the passengercompartment, one ,of whichis used only'linthesurnmer- `time tonintroducefresh air into the car. 'It Vvis y'provided with` a Vbi1il'erily valvemanually adjustable 'from the dashboard. 'The other duct is .usuallyprovided with a small blovverl andis used in connection `with a heaterheated by hot water from the engine jacket. The introduction of freshoutside air `for heating has numerous Vadvantages over all recirculatngsystems `in that it tends to eliminate condensation of moisture .onthewindshield ,and Windows, and to eliminate the accumulation of cigarettesmoke and stale air. On the other hand, the use of the ram duct enhancescertain of the problems by virtue of the fact that the air `velocitythrough the ram duct Varies With the speed `of the car, and-of .coursewith the speed and `direction of the wind. Thisis, to some extentcompensated for bythe small'blower in the ram duct. 1 a, a,

In considering the4 problem of car heating the most important factor tobe considered `is that having to do with the temperature ofthe aircoming from the heater. With the recirculation of air ,through thepassenger compartment determined by the introduction of fresh outsidethe passenger compartment` air through a slightly cracked rear Window,the actual car temperature at any instant isprimarily a function of thetemperature of the incomingair ,from the heater into the passengercompartment. It has been found by experiment that the incoming Vair fromthe heater should be slightly Warmer than the desired car temperature tocompensate for heat losses from `the car. However, fluctuations in theair temperature coming from the heater must be held to a minimum toinsure maximum comfort. I have found, `in connection with a l1949 Ford,for example, that with an outside temperature of'about 25 F. theoutlettemperaturefrom the heater should be about F. in order'to maintainapproximately a '75 F. cartemperature. These figures will vary slightlywith other makes of automobiles, and` have been given only by Way ofexample. Y

,A study of the relationship between outside air "temperature, vram airtemperature, water .temperature in andout Aof the heater, airtemcreases, the proportionate relationship from a heat balancestandpoint does nothold throughout the normal ,driving speeds ofanautomobile.

With the foregoing considerations in mind it is an object of the presentinvention toI provide a car heating system in which the temperature ofthe passenger compartment is controlled by controlling the temperatureof the air coming out of the heater. It is another object of theinvention to control the temperature of the air coming out of the heaterby controlling the ow of water through the heater.

It is still another object of the invention to control the flow of waterthrough the heater on the basis of the temperature of water coming fromthe heater.

It is thus an object of the invention to provide a thermostat in heatexchange relationship with the hot water leaving the heater and causingsuch thermostat to control a valve which determines the flow of hotwater through said heater.

It is a very important object of my invention in achieving the mostperfect car temperature control as mentioned above, to provide anadjustable valve seat for said valve and to provide a second thermostat,exposed to car air temperature, to adjust the position of said valveseat.

These and other objects of the invention which will be pointed out inmore detail hereinafter, or which will be apparent to one skilled in theart upon reading these specifications, I accomplish by that certainconstruction and arrangement of parts of which I shall now describecertain exemplary embodiments. While I have illustrated the invention inconnection with a heating system of the type where fresh outside air isintroduced through a ram duct, it will be understood that my inventionis equally applicable to a recirculating type of system. Throughout thespecification and claims where the term water is used, it is to beunderstood to include water containing antifreeze in any concentrationup to and including 100%.

Reference is made to the drawings forming a part hereof and in which:

Figure l is a diagram representing the ow of water and air in a heatingsystem according to my invention;

Figure 2 is a cross-sectional view through a thermostat and valveshowing a portion of the heater and a manual control;

Figure 3 is a fragmentary View similar to Figure 2 showing a differentway of mounting the thermostat;

Figure Li is a fragmentary view similar to Figure 2 showing the manualcontrol replaced by a thermostatic control;

Figure 5 is a fragmentary view similar to Fig'- ure 3 showing yetanother way of disposing of the thermostat in relation to the heater;

Figure 6 is a fragmentary cross-sectional view through a valve seat ofmodified construction;

Figure 7 is a fragmentary cross-sectional view of an arrangement inwhich the thermostat is subjected to the outlet water temperature, whilethe valve controlled thereby is in the inlet water line, and

Figure 8 is a graph showing temperature-time curves for engine water,air out of heater, and

.car air with different controls.

In the diagrammatic representation of Figure 1 the engine is indicatedat Ill and its radiator at II. A circuit of water from the engine jacketthrough the radiator is indicated by the pipes I2 and I3. A pipe I4leads hot water from the engine jacket to the heater indicated generallyat I5, from whence the water returns through a pipe I6 to the engine I0! l1 deSgnates a ram duct provided with a buttery type valve I 1a, anda blower I8 through which fresh outside air is supplied to the heaterI5. The control valve and thermostat are indicated generally at I9 and amanual control for the valve seat is shown at 20, and a manual controlfor the valve IIa is shown at 20a. The basic theory and feature of thepresent invention is illustrated in connection with Figure 1. It will beobserved that the thermostat is placed at the outlet of the hot waterfrom the heater and that it controls a valve at the outlet from theheater so that the flow of water through the heater is regulated by athermostat responsive to the temperature of the water leaving theheater. Thus, if the outside air is cold and abstracts more heat fromthe water in the heater, the outgoing water will be colder. In responseto the drop in temperature of the outgoing water the thermostat willopen the valve to permit more hot water to flow through. Conversely, ifthe outside temperature is warmer so that the heater abstracts less heatfrom the water, the thermostat in response to the warmer temperature ofthe outgoing water will close the valve so that a small ow takes place.The same situation obtains if the entering air temperature is constantbut the mass of the air flow increases or decreases; this will have theeffect of lowering or raising the outlet water temperature respectively.

Referring now to Figure 2, I have shown a conventional car hot waterheater having an inlet heater 2|, an outlet header 22 and a core 23. Thecore will generally be composed of a plurality of slender tubes throughwhich the air flows and through which the heat from the water istransferred to the air. Water flows through the heater in the directionof the arrows in Figure 2. The outlet header tank 22 is provided with anaperture 24 into which the sensing element 25 of the thermostat extends.The thermostat I prefer to use is one available commercially under thename Vernatherm. This thermostat has a cup element indicated at 25 whichis lled with a heat sensitive material which undergoes a molecularrearrangement under the influence of heat. The thermostat has a piston26 which is thrust out from the thermostat under the iniiuence of theincrease in temperature.

The thermostat is held in a cup-shaped element 27, which is providedwith apertures 28 for the passage of water. The piston 26 is connectedto a valve stem 29 of a valve 30. The stem 29, -or the piston 26, isprovided with a shoulder 3l. The cup-like member 32 embraces thethermostat and is provided with a ange 33 and has a hole for the passageof the valve stem 29. The cup member 21 is secured to another cup-likeelement 34, as by silver solder or the like at 2lb, and a compressionspring 35 bears at one end against the member 34, and at its other endagainst the flange 33. The cup member 21 is flanged at 21a in order toseat the sensing element 25. The spring 35 serves as a spring return forthe thermostat.V It is a characteristic of this type of thermostat thatwhen the sensing element is cooled down the piston thereof must beforced back since it does not return of its own accord. The valve 30 isprovided with a disc 38a, which may be of synthetic rubber or similarmaterial.

A thermostat and valve housing 36 to which the cup members 34 and 21 aresecured, as by silver solder o r the like at 34a, is screwed orotherwise suitably attachedLto the outlet header tank as shown.

The housing 3,6 is'provided With an outlettting'y 31'1 and` carries on.its' interior a valve seat member-38. The valve seat member is providedwith asuit'able sealing means as indicatedat 39l and` has a conicalvalve seat 4U. In order that thel closing of'y the: valve may take placegradually', If have` found thatH the ideal apexangle of theval've seatisi on the order of 40. In other Words, anyr element of. the conicalsurface Ml makes an angle of"` about' 20 with the axis of" theN valve'.This angle is based on the motiontemperaturecurve of the thermostat and'the heating requirements of `the car, so as to achieve fairly constantair-out temperature regulation even with relatively high loutsideairtemperatura.

and to avoid" violent cycling of the` air-out temperature` which wouldresult from repeated openingfan'dclosing the valve. The frusto-conicalsur,-

face All-merges by means off a curve 4l into, a

cylindrical portionll'rwhich is of a, diameter to nt snugly' thediameter of the disc 39a.. The valve seatv is provided' with a meteringgroove 43. which extendsirom a point in the conical surface justoutside` the curve M to a point in the cylindrical' surface .42: atadepth of about twice the thickness of the disc 3llaso that when the discaA is entirely. closedfin the cylindricalportion d2 a very slight' flowof hot water can still pass through the valve, whereby the sensingelement 250i 'the thermostat will respond morev By adjustment of` thehandle 49 to be described hereinafter it` is possible to shut 01T thevalve entirely also by moving the valve seat member to a pointiwhere`vthe disc. 36a is in contact with` the` unbroken cylindricalsurfacebeyond theA metering groove..

InnormaLdriving, however, the disc v3fm never quite entersthecylindrical' portion e2. Also, in normal` driving with relatively lowoutside temperaturethe metering groove isof Ano signincance becausevitsA cross-sectional` area is substantially negligible inrelationy tothe flow area. of4 the valvey in the regioni of the conical surface t9,When,vhowe.ver, theV outside air temperature is relatively high, say,from40 to 50 F. andaslight amount'vofheatingis desired, the amount offlow of water. through the4 heater willy be extremely small;. it.mayamount,` to apint per` minute, or evenless. The metering Voi. sucharsmall flow of Water presents many difiiculties. eter.y ofl thee-valveAseatand.. disc` were `,made much smaller,l thesmetering onlow atsuch,relativelyA high outside temperatures would not be-agreat problem;But in order-v to,l provide. suficient'riow where;maximum; heating isrequired. those di-` ameters must.berelativelyflarge. Thus, with thevalvez designed `for maximumperformance, where thetoutsideairtemperature is -relativelyfhigh the valve will falternatelyfopen andclose; During; its.v closed'v position., all;` flowf of?. Water.through; the: heater: Williston` and .ther air f temperature; out? oi;

If the diam-V theheater will dropY rapidly in a matter of a few secondsItdanuncomfortabledegree; Thefmete'- inggroove 43 comesinto-playl-whenthe disc 30"is almost at'v the; point'I of" engaging thelcylindrical surface 42', and perm-its a very slight. now of water-whichIhavef'oundwillprevent the violent cycling which is' objectionable.

The valve seat member 38 isiofl generally cup'- shape and" is providedwith they passages 44 for the Water passing through theyvalve. The Valveseat member issuitably securedto a controlmember indicated: generally at45, `which isA provided` with a threadedportion WhaVingfthreaded engagem'ent: in an extension AFl off the housing'.

Suitable sealing means for the member 45" are providedv as at 48' andahandle member' is` pro-v vided at 49.' Itwill be' observed that arotation of the handle member.l 49 serves to adjustlthe positionoffthefva'lve seatu member 38 in relationv to the valvedisc- 3 0. Thehandle member' 48 which. corresponds tothe member 2t of Figure 1 maylextend into the passenger compartment sov that the operator may,nmanually adjust' the tem*- perature at which; the valve will. close: Byadjustmentpof thehandle memberj lllthevalve seat can be retractedto"thepoint that the valve cannot,v close, lregardlessof;watertemperature:vSima ilarlythe valveseat: can be advanced to'thepoint where the' valvevcannot Aopen no matter how-cold, Y the water in the outlet header tankmay get.

Thus the operator has' complete," control Aover the heater and canoverride the thermostatif` he dee sires,

In` Eigureil have shown a modification inlthe mountingv of thethermostat'onA theoutlet header tank. As Jthere shownia'wall of'ltheoutletheader tanl;` is providediwit'h a depressionY titr` of a size toaccommodate: the sensing;l element 25" of' the Arr apertureis` providedin a Wall heater flows intotheivalve; For this purpose also' the holer28 in the cupmember 21'is made to regis ter withthe-duct 36a: In allother respects the arrangement of Figure 3; is the same as' that ofFigure 2. In many cases/it will be aV cheaper installation in themanufacture of the heater to provideadepression' 50, rather' thanv toprovide a largehole into which the entire unit extends asshownin Figure2; y

In Figure 4 I haveI shownV a slight mcdication inWhichthevalveseatm`ember'38 is' adjusted as toits position automatically bym'eans oi asecond thermostat indicated generally`- at 52. The thermostai; 52subjected tocar air temperature; and

its piston 53, bearsagainst a rodv 45a which isv secured to the valveseat:` member 38; As1described above a compression spring 54 bearsagainst the end of the-housing 361at one end and againstltheshoulderi45h onthe rodll'a. The purpose'fof this spring Aendisito return thepiston 53."1 when the car:l air: temperature" drops; only-diiferencebetweenrthestructure of; Figure 4 and that:r of Figure v2 Vis thatIthe:v position of the valve seaumember 38isth'ermos'tatically conetrolled ratherthan manuallyA controlled. However; the' thermostatzcanbescrewed in. or out manuallytosgive-thevoperator the same-overeride;

feature disclosed above in connection with the memberftSf In Eiguref Ihave shown-yetanother.l modica- The contact one or more of the tubes 55through which the air to be heated ows. Thus, the sensing element of thethermostat is not only in heat exchange relationship with the hot waterflowing through the outlet header tank, but also in heat exchangerelationship with at least one of the airliow tubes therein. Theexternal portion of the mounting may be as disclosed in any of the otherfigures. While I have shown the valve and thermostat in or immediatelyadjacent the outlet header tank, in some cases it may be found desirableto install them in the hose line leading from the outlet header tankback to the engine. While such an arrangement is not as good or as cheapas any of those shown, it is of course within the scope of my invention.Installation costs will be lower when the valve and thermostat are apart of the heater unit.

In Figure 6 I have shown a modification in the valve seat structurewherein the valve seat is no longer cup-shaped as in the other figures,but is provided with a boss t which is provided with the apertures 51for the passage of Water. A manual control element is again indicated at58. This may be similar to that shown in Figure 2. In Figure 6 theconfiguration of the valve seat is more clearly shown and the referencenumerals are the same as those used in the description of Figure 2.

In some present day automobiles, the Water Y pump which producescirculation of the water through the engine jacket, radiator and heater,is such that, under certain conditions, a pressure as high as pounds persquare inch is built up. In such cases it will be desirable that thevalve controlling flow through the heater core be on the inlet side ofthe heater. According to my invention, however, it is necessary that thethermostat still be subject to the outlet water temperature.

I have shown in Figure 7 an arrangement of this kind. Wherever possiblethe reference numerals identifying certain parts are the same as in theother figures. The thermostat 25 with its piston 26, the valve stem 29aand valve disc 39a, the valve seat member 38a, and manual control shaft45, are incorporated in a generally tubular housing having ports 6I and62 which are connected by the nipples E3 and S-i to the inlet and outletheader tanks 2l and 22 respectively. rlhe valve stem 29a is elongated sothat both the valve and seat members are to the left of the inlet port6l, While the thermostat is to the right of the outlet port 62. Betweensaid ports is a dividing element having its ange E6 welded or otherwisesuitably secured to the walls of the housing 60. The member 65 isprovided with a bearing boss El for the valve stem 29a. The thermostatis held in place by means of a `snap ring 68 bearing against aperforated annulus S9, which in turn bears against the annular bead l0.The spring 35, bearing at one end against the member 65, bears at itsother end against the member 32, which in turn engages the shoulder 3lon the valve stem. The valve stem is sealed against its bearing boss 61as indicated at Il. The outlet hose connection is made to the outletnipple 12, and the inlet hose connection to the inlet nipple I3.

From the above description it will be clear that the Water entering theheater passes first through the valve and then into the heater core.The'outlet water'ilows'past the thermostat as before, and the thermostatdirectly actuates the valve. The major diiference in this arrangement isthat the valve is on the inlet side of the heater instead of the outletside.

In Figure 8 I have shown time in minutes plotted against temperature indegrees F., showing the engine water temperature curve rising steadilyuntil it reaches about 180 F. in about 10 minutes, after which it cycleswith variations in engine speed and air speed. Where the manual controlis provided and is not used, the air out of heater temperature rises to,say, F. in about 8 minutes, and then holds at that leveLwhile the carair temperature rises very slowly and does not reach substantially '70F. for about 20 minutes. On the other hand, where the arrangement ofFigure 4 is used the air-out of heater temperature is brought rapidly upto about, say, F. in a matter of 10 minutes, and therefore the car airtemperature rises much more rapidly and will reach 70 F. in about 9minutes. Then the car air thermostat regulates the valve seat so thatthe air out of the heater temperature is reduced to about 110 F., whilethe car air temperature is held at 70 F. The same result substantiallymay be accomplished by actuating the manual control, but the operator islikely to forget to return the manual control to normal position, withthe result that the car will be overheated. The temperatures and timesgiven above are exemplary only and do not constitute a limitation uponmy invention.

While I have described various details of construction, it will beunderstood that these may be varied considerably Without departure fromthe spirit of my invention. The basic principle of my invention is theprovision of a thermostat having its sensing element in heat exchangerelationship with the hot water leaving the outlet header tank of a hotwater type car heater and having a valve for controlling the ow of waterfrom the outlet header tank, which valve is operated by the thermostat.In this Way the outlet temperature of the water passing through theheater can be quite accurately controlled and, as discussed hereinabove,it is the accurate control of the outlet Water temperature which enablesme to control accurately the air-out temperature from the heater. Again,as pointed out above, accurate control of the air-out temperature of theheater leads to accurate control of the air temperature in the passengercompartment. The thermostat being subjected to the temperature of thewater in the outlet header is almost instantaneously responsive tochanges in that outlet water temperature, and therefore the now of waterthrough the heater is immediately controlled, and thereby thetemperature of the air is immediately controlled. I have found that thisimmediate control ofthe air-out temperatures enables me to maintain asubstantially constant temperature in the passenger compartment.

It will therefore be understood that the various details are not to beconsidered in any way as limiting otherwise than as set forth in theclaims which follow.

Having now fully described my invention what I claim as new and desireto secure by Letters Patent is:

1. In a hot Water car heater, a thermostat having its sensing elementdisposed in heat exchange relationship with the water as it leaves theheater, a valve for controlling the flow of Water through said heater,said valve being operated by said thermostat and having a movable seatand means for moving said seat, said valve'being of disc form and saidseat being of frusto-conical form merging into a cylindrical form of adiameter sub- Y sensing element of said thermostat is also in heatexchange'relationship with anair iiow tube in said heater.

4. A device according to claim 1, in Which said heater has an inletheader tank, a heater core composed of a number of tubes through whichthe air to be heated ows, and an outlet header tank, and in which a wallof said outlet header tank has a cup-like depression, said thermostatbeing mounted on said Wall with its sensing element in said depressionand in heat exchange relationship through said Wall with the water insaid outlet header tank.

5. A device according to claim 1, in which said means for moving saidseat comprises a second thermostat having its sensing element in heatexchange relationship with the air in said car, and operativelyconnected with said Valve seat,

whereby to adjust the position of said valve seat in response to changesin the air temperature in said car.

6. A device according to claim 1, in which said means for moving saidseat is manually operable.

7. A device according to claim 6, in which said valve is disposedadjacent the outlet from said heater.

8.v A device according to claim 6, in which said valve is disposedadjacent the inlet to said heater.

ALLAN C. HOFFMAN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,850,963 Sponar Mar. 2'2, 19321,906,994 Medine May 2, 1933 2,019,303 Hall Oct. 29, 1935 2,065,148Nallinger Dec. 22, 1936 2,075,498 Bondurant Mar. 30, 1937 2,213,018Perkins Aug. 27, 1940 2,273,000 Hans Feb. 10, 1942 i 2,300,011 Rose Oct.27, 1942 2,470,503 Levine May 17, 1949v 2,480,676 Shaw Aug. 30, 1949

